Question: Simplify the following expression: $z = \dfrac{10r}{9} + \dfrac{3r}{10}$
Explanation: In order to add expressions, they must have a common denominator. The smallest common denominator is the least common multiple of $9$ and $10$ $\lcm(9, 10) = 90$ $ z = \dfrac{10}{10} \cdot \dfrac{10r}{9} + \dfrac{9}{9} \cdot \dfrac{3r}{10} $ $z = \dfrac{100r}{90} + \dfrac{27r}{90}$ $z = \dfrac{100r +27r}{90}$ $z = \dfrac{127r}{90}$